A major objective in these investigations with Sindbis virus is to elucidate the molecular basis for the origin of defective-interfering particles and to define the mechanisms by which they inhibit the replication of standard virus. We are currently examining the structure of the defective RNA using competitive hybridization and oligonucleotide mapping. A second goal is to examine the glycoproteins and lipids of Sindbis and VSV passaged in mutationally-altered host cells. These studies will attempt to define the role of these components in the structure and biological activity of RNA enveloped viruses. BIBLIOGRAPHIC REFERENCES: Kennedy, S.I.T., C. J. Bruton, B. Weiss and S. Schlesinger. Defective Interfering Passages of Sindbis Virus: Nature of the Defective Virion RNA. J. Virology 3: 1034-1043 (1976). Leavitt, R., S. Schlesinger and S. Kornfeld. Tunicamycin Inhibits Glycosylation and Multiplication of Sindbis and Vesicular Stomatitis Viruses. J. Virology 1: 375-385 (1977).